You know... if you have closed polys at their correct Z elevation, you could just use the LOFT command, introduced in 2007, to create a solid from those cross sections, and in the properties of this new object, it'll tell ya the volume. Pretty sure it tells you the volume there, I'm too lazy to test it. If it doesn't show it there, I -know- it'll show it on the MASSPROP readout, amongst 103854 other stats for the object that you would never care about.